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By P Revell, G Wilkie, P Walters, L Keeney, F Faramarzi

Grade Engineering® is a value-driven strategy aiming to maximise benefits by exploiting intrinsic grade variability of ore deposits. It utilises a multitude of separation techniques to remove low grade material before being introduced to post-blast size reduction processes, i.e. crushing and grinding. At an operational scale, Grade Engineering® techniques can be implemented at the drill-and-blast stage, to control the degree of fragmentation in accordance with the spatial distribution of valuable minerals across an ore domain through differential blasting. It can also exploit intrinsic textural and breakage characteristics of a given ore type to reject uneconomical barren material at coarse sizes, which is known as Natural Deportment. Grade Engineering® can also be employed in the deliver stage of the mining value chain through sensor-based bulk and particle sorting. Each strategy is therefore highly dependent on the responsiveness of an orebody to available techniques. That is, the extent to which Grade Engineering® drivers would be capable of unlocking potential values of currently un-amenable orebodies depends on how detailed the heterogeneous nature of ore domains can be described. This paper considers exploring possible linkages between deportment characteristics of an ore and its competence when broken in a range of energy inputs at a particlebased level. Accordingly, potential opportunity may lie in exploring whether the intensity of input energy (or degree of fineness) can be used as a lever to improve or ‘unlock’ ore amenability to Grade Engineering® techniques. Implications from such a detailed approach offers new opportunities to enhance Grade Engineering® gains through engineering ore competence variability.

Nov 10, 2020

By S Warden, T Neville, P Leckie

At its simplest, the classification and characterisation of an orebody is a matter of Where, What and When. Where and with what spatial resolution are measurements taken, What properties are measured, and When are the data acquired, processed, and delivered to create the most value. This paper delves into how existing and near-term advances in measurement technologies, field automation, and whole-system-digitisation are combining to open new routes for mine and exploration productivity improvement. Commencing when the initial exploration hole is dug, the advancement in deployment of survey technology—from expert-operated, to driller-operated, to driller-integrated—is used to demonstrate a template for adoption of higher technology measurements. We then introduce and discuss the multi-use measurement as offering outsized returns from a single measurement run, highlighting two new technologies that acquire rock strength while drilling and downhole assay data as examples. For rock strength, we highlight a novel approach to determining Uniaxial Compressive Strength (UCS) while drilling, its relationship to and advantages over Mechanical Specific Energy (MSE), and how it offers utility to multiple downstream processes. For downhole assay, we detail how a back-tophysics approach to Pulsed Fast and Thermal Neutron Activation (PFTNA) analysis offers significant advantages over other measurement methods and earlier implementations of PFTNA, generating a rich data set that can significantly extend and improve the information on which mining decisions are made. Finally, we discuss the possibilities enabled via optimising data delivery, collection, and curation— noting a fundamental limitation of historical systems and exploring the possibilities that will be unlocked by soon-to-market solutions that better enable Orebody Characterisation data to (virtually) move in space and time with rock material post-blasting. Ultimately, the value of optimising the Where, What, and When from point of measurement to the moment it generates maximum value will create greater life-of-asset production for a lower cost and energy input.

Sep 1, 2024

By C Jenkins, M Mativenga, C Stanton, J Gerber

In 2014, Arrium completed an optimisation program on its magnetite concentrator, enabling a reduction in the overall cost base of producing concentrate through an increased ability to treat a wider range of ore types, previously considered waste. The development was the culmination of four years of work, conducted in house by Arrium’s mining development group. The overall intent of the plant design focused on improving the concentrator’s ability to treat a wider range of magnetite ore types. Metallurgical analysis of these feed ore groups outlined a need for more grinding power if production quality was to be maintained and throughput increased. As such, a tertiary grinding circuit was designed which, alongside the rectification of key operational bottlenecks, would allow the plant to continue to produce concentrate at the required specification and rate. The technology chosen for the tertiary grinding application was the XT IsaMillTM, which is known for efficient fine grinding when compared to conventional ball milling. The transfer sizes between the existing comminution circuits were coarsened, allowed for the treatment of different ores at the required rates. The optimisation project was successfully completed in February 2014 after a three month commissioning phase. The initial metallurgical testing and engineering of new equipment proved highly successful with all equipment meeting or exceeding design parameters.CITATION:Stanton, C, Mativenga, M, Gerber, J and Jenkins, C, 2015. Unlocking plant capability through targeted debottlenecking of Arrium’s magnetite concentrator, in Proceedings Iron Ore 2015, pp 185–190 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By X Li, W McKeague, M S. Powell

This paper explores the importance of operators in the overall efficiency of mineral processing plants. With the potential of future control configurations becoming more remote, it is time to review the implementation of control and utilisation of operators. This paper is based on a preliminary review of operators and control room operations and clearly shows that, in the minerals industry, operations are typically run in a reactive mode (with a focus on ensuring equipment operation), rather than in a proactive mode (with a focus on optimising the process performance). The primary reason for this misguided approach is the short sighted thinking applied to the challenges of designing technology and organisational tools capable of addressing the essential operational needs: an approach which inevitably results in a disconnect between people and technology. Contrary to the popular approach of replacing operators with expert systems, the thesis of this paper is that the shift to more complex circuits, with higher demands on processing capability and control, will require the actual upskilling of operators. Experience in mineral processing and other industries indicates that expert systems cope well with small changes but are typically unable to respond to major changes in feed material and this is where the expert operator becomes crucial. Providing operators with ongoing high level training in process understanding, and restructuring how they interact with the plant and interface with the control system is the approach being proposed here - an approach surprisingly underutilised and often absent in the minerals industry today.CITATION:Li, X, Powell, M S and McKeague, W, 2012. Unlocking processing potential by empowering our operators, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 333-340 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By B Haase, R Saha

Conditional simulation (CS) has been extensively used in metal industry to assess uncertainty of geo metallurgical variables to build robust distributions around grade tonnages across different time horizons. Coal’s entry to nonlinear stochastic modelling is relatively new and this paper summarises the work done at BHP to enable its practical usage from production time frames to Life of Asset planning. CS in coal using Sequential Gaussian Simulation (SGS) is used to understand resource confidence around specific variables within pre-defined boundaries of spatially continuous domains for each coal seam. The variation between simulations for a given parameter reflects uncertainty. This paper demonstrates the use of CS to profile resource based upon agreed seam/parameter uncertainty thresholds which affect planning, forecasting, extraction and inform identification of key production risks and defining mitigation strategies. The end goal is to de-risk long-term plans by optimising infill data collection and improve stability in short-term planning through increased understanding of confidences locally rather than at global resource definition stages. The paper also briefly discusses the use of automated workflows and systems to minimise the time spent on the process to enable use in decision-making.

Mar 22, 2022

By J Siliézar

The Ernest Henry Mine (EHM) is situated 38 km north-east of Cloncurry in the Mount Isa – Cloncurry mineral district of northwest Queensland. The EHM orebody is an iron oxide copper gold deposit with an average grade of one per cent copper, 0.5 g/t gold and 23 per cent magnetite, with current reserves of approximately 88 Mt.The copper concentrator is a single line plant with a nominal throughput rate of 1300 tonnes per hour. An average of 350 000 tonnes of concentrate is produced each year containing around 100 000 tonnes of copper metal and 120 000 troy ounces of gold.In December 2009, Xstrata Copper announced approval of a $589 M investment to extend the life of EHM to at least 2024, through the transformation of open pit mining operations to a major underground mine together with the construction of an associated magnetite extraction plant.The EHM magnetite plant extracts the magnetite from the copper concentrator’s tailings stream. It will produce approximately 1.2 Mt of magnetite concentrate per annum at full capacity for export to Asia, making EHM Queensland’s first iron ore concentrate exporter. Construction of the magnetite extraction plant commenced in July 2010 and was completed in January 2011.This paper gives an overview of the development of the EHM magnetite extraction plant flow sheet from the early mineralogy and laboratory test work through to the plant commissioning and early operation of the base plant. It has a major focus on the commissioning learnings from the plant start-up and includes a review of the operational performance of the plant versus original design and expectations.

Jul 11, 2011

By R. Jacob Cefalo, Miguel Valenzuela

The modern drill and blast engineer operates in an environment often rich with data from drilling data and blast designs vs. actuals to fragmentation distributions and vibration records. Despite this abundance, much of the information generated remains underutilized, often collected as a matter of routine rather than for a means to an end. This paper explores how artificial intelligence (AI) can bridge that gap, transforming raw operational information into actionable insights that lead to more consistent and optimized blasting outcomes. Through AI-driven analysis of drilling logs, burden and spacing measurements in design vs. actual, fragmentation distributions, and vibration records, we can identify hidden patterns and correlations that traditional analytics overlook or that we may not be aware of. These insights enable engineers to proactively adjust designs and loading strategies, ultimately improving performance aspects such as improving fragmentation, minimizing ground vibration, and lowering overall operational costs. The paper examines the industry's reliance on lagging indicators, such as post-blast fragmentation surveys or actual powder factors, and suggests the need to shift toward leading indicators like real-time drill data monitoring and predictive fragmentation modeling. Utilizing AI to forecast outcomes before a blast is carried out allows engineers to take corrective actions early in the process, thereby creating a feedback loop that continuously improves performance. This integration of AI into drilling and blasting practices marks a pivotal opportunity for the explosives engineering field to evolve from reactive to predictive methodologies unlocking a new level of operational intelligence and value creation.

Jan 26, 2026

By Lawrie Logan, Mike Wiggin

This paper will be in two parts, a discussion of the benefits available from benefit sharing as a concept followed by an examination of how this approach was applied at Mesa J Mine and what improvements were made. The first part is an outline of the ways that both parties in a benefit sharing agreement can uncover additional wealth by bringing a new approach to the relationships between mine and supplier. The paper describes a partnering agreement recently established between Robe River Iron Associates (RRIA) and Dyno Nobel Asia Pacific Ltd (DNAP) to access the wealth locked up by the usual explosives supply contracts in Australia and elsewhere. The partners are acting cooperatively to maximise the benefits to both parties from optimising blasting practices at the Mesa J Iron Ore Mine in the Pilbara region of Western Australia.

Jan 1, 2001

By S Gulati, N Sarkar, T Vink, S Battersby, L Okada

This paper examines a successful project implemented by BHP Mitsubishi Alliance (BMA) and the Polymathian team at Deswik, aimed at enhancing short-term scheduling processes to reduce vessel turn times in the BMA Central Queensland coal value chain. The project’s objective was to digitalise the planning process to enable planners to make data-driven insights to improve the profitability of the value chain. The strategy involved developing a digital mining system that incorporates data storage, cloud computing, and the ability to meet the integration needs of both internal and external business systems. This was complemented by a sophisticated, optimisation-based, decision-support tool to enhance the planning teams’ ability to make timely and effective decisions.

Sep 1, 2024

By P. Tolvanen, A. Jalili

"When hard times strike in the mining cycle, sites tighten their belts and focus on lowering their unit costs. Lower unit costs can be achieved by reducing expenditure, increasing production, or by a combination of both. Faced with these requirements, site personnel must turn to areas where they can focus their effort for maximum return. For many sites, both in Canada and overseas, focusing on improving flotation cell maintenance is one of the areas where gains can be made for minimum outlay. Due to resource limitations and/or lack of equipment understanding, maintenance on many sites is only conducted on a reactive basis, once equipment fails. This paper will promote the idea that mineral processors should become more familiar with their equipment so they can ensure that the plant’s ability to produce is not compromised. By better understanding the flotation equipment and ensuring the critical components are maintained, it should be possible to unlock value in an operation. Flotation equipment inspections will be discussed in detail, including key items to look for during these inspections. Potential approaches for predicting wear and change-out time for flotation equipment components will be also demonstrated. An example of one approach used at a South African nickel site will be given.INTRODUCTIONWith metal prices decreasing and operating costs rising, concentrator operators are looking for ways to improve their bottom line. Lower unit costs can be achieved by reducing expenditure, increasing production, or by a combination of both. To meet the expectation of shareholders, mineral processors must turn to areas where they can get the best return for their efforts. One area where there is a large opportunity for improvement is in the maintenance of flotation equipment.On many mine sites, both domestically and around the world, it is quite common to see the philosophy applied of repairing equipment only once it has failed. Though some sites have advanced enterprise management systems and monitoring programs, in the authors’ experience, the decision on flotation equipment maintenance is rarely made on a proactive basis. Two common trends that are evident in the mining industry are that operations are under pressure to keep the plant producing, and maintenance managers generally have very strict budget targets to meet. In addition to these factors, few sites have a good understanding of the financial implications of running with worn or broken flotation equipment. Knights, Jullian and Jofre (2006) summarize this situation well, stating that the lack of correlation between some commonly used maintenance performance measures and key business drivers can lead to maintenance being seen only as a cost center (that needs to be reduced) rather than a tool for productivity improvement."

Jan 1, 2015

By A Grace, C Sennersten, T Taylor, A Davie, R Lyu, D Pentecost, C A. Lindley, J Craig, L De Macedo Camargo

Many underground mine void spaces are not suitable for human entry due to unprotected roofs, instability or having an unknown safety state (eg if they are many decades old). Investigations of these voids may nevertheless be important for general mine safety, for example to detect propagating collapses or water accumulation, prevent accidental intrusion by new developments or drilling to reassess old spaces for re-mining. Robots are an ideal technology for investigating these spaces, especially flying, rotary-wing robots that can access and map vertical structures and spaces while avoiding rocks, water and mud that have accumulated on void floors. To operate in underground mines, we are developing customised unmanned aerial vehicles (UAVs) as well as interactive 3D virtual models of the vehicles and their underground environments for controlling vehicle operation and visualising incrementally gathered survey data. Using a game/simulation engine to provide an interactive interface for UAV operation makes it possible to orchestrate external spatial information and video feeds with in-game cameras for optimal visualisation that is not limited to the position, orientation or field of view of cameras mounted on the UAV. First and third-person points of view with respect to the UAV are provided, together with 2D and 3D gaze tracking to provide effective interfaces for geology and mine engineering experts without the need for specialist UAV piloting skills. Ongoing work is addressing the provision of greater levels of autonomy for these vehicles to support mapping well beyond the line of sight of operators and geological characterisation of rock surfaces using sensors mounted on them, including miniature X-ray fluorescence and Raman spectrometers. Gathered data is fed into more general 3D models of the mine, block models and orebody so that the UAVs function as elements of a mobile perceptual system for intelligent mining.CITATION:Sennersten, C, Lindley, C A, Davie, A, Lyu, R, Grace, A, Evans, B, Pentecost, D, Taylor, T, De Macedo Camargo, L, Craig, J, Salomao, G N, Hellicar, A, Biggins, D, Timms, G, Coombe, M, Shahriar, M S, Smith, G and Rahman, A, 2015. Unmanned aerial robots for remotely operated and autonomous surveying in inaccessible underground mine voids, in Proceedings Third International Future Mining Conference, pp 101–108 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

"9.1. IntroductionThe application of the electron microprobe for in-situ analysis of platinum-group minerals (PGM), first reported by Borovskii et at. (1959) and Genkin (1959), has resulted in a large and growing number of analyses of unidentified PGM. Figure 9.1 charts the increase in the number of reported unnamed PGM from 3 in 1959 to a total of 140 by 1979. All these minerals, with the exception of UN1968-5 and UN1976-1, were analyzed with the electron microprobe.There has been no recognised or consistent manner for reporting these unidentified PGM. The term ""unnamed"" has been used for PGM that are considered to be new species without a name as well as for PGM which have not been exhaustively compared to named and unnamed PGM in order to determine whether they are unique. Many of the so-called unnamed PGM are only unnamed because of poor microprobe analyses or because larger than usual elemental substitutions (e.g. Bi for As) made it difficult to calculate the true stoichiometry. Some of these unnamed minerals have been unnecessarily reported with non-stoichiometric formulae, as discussed by Cabri (1980). Better analytical data should reduce the number of such proposals.Another unfortunate practice, possibly used to by-pass the scrutiny of the Commission for New Minerals and Mineral Names, I.M.A., is to report a ""new"" mineral by referring to it by a name made up of its constituent elements. This has been deplored on a number of occasions (cf. discussion in Fleischer et at., 1976, p. 179), but some journals continue to publish such material. The Commission on New Minerals and Mineral Names has not recognised such ""names"" and these PGM are therefore included in this chapter with other unnamed minerals.A further example of inconsistency in reporting unnamed minerals is the report of a specific ideal stoichiometry with no further details (not even an analysis!); sometimes with a note that this will be reported in greater detail in due course. I have also been guilty of similar optimistic statements and, unfortunately, it is not always possible to follow through. Some authors give data on unnamed minerals in such a discrete manner that their reports are sometimes missed in literature searches."

Jan 1, 1979

By Evan Brinkerhoff, Steve Chorley

The largest hard rock TBM ever to bore in the USA, an 11.6 m diameter Robbins Main Beam TBM, recently underwent a planned in-tunnel diameter change to a more compact 9.9 meters. The first-of-itskind conversion process for the Main Beam TBM was undertaken 2.8 km into the bore and was not done inside a shaft or pre-excavated portal. This paper will detail the unique dual-diameter machine designed for the Mill Creek Drainage Relief Tunnel in Dallas, Texas, USA, machine performance, and successful size conversion process that took place in early 2021—a process that utilized the four C’s of construction to enormous benefit: Communication, Cooperation, Collaboration and Coordination.

Dec 1, 2022

By J Lainé, M Badawi, A C. de Araujo, Y Foucaud, C Veloso

Flotation is the one of the most used techniques for the mineral separation of non-ferrous ores worldwide. However, the increase of the complexness along with the decrease of ores liberation sizes ought to become important challenges for mineral processing, including flotation. It now appears necessary to better understand the fundamentals of the flotation process, particularly the adsorption of flotation reagents at the liquid/mineral interfaces, to propose further improvements. Flotation relies on different phenomena: surfactants adsorption, on one hand, and collision, adhesion, and transport of particles with bubbles, on the other hand. For acknowledging the reagents adsorption mechanisms, molecular modelling tools borrowed from chemical and material sciences, are increasingly used. Atomistic simulations were successfully applied to study the flotation reagents interaction with various mineral surfaces, eg of two common minerals from iron ores, kaolinite, and magnetite surfaces, or with fluorite surface, a tungsten ores common gangue mineral.

Aug 24, 2022

By A Manfrino

The Iron Bridge magnetite mine and infrastructure project is currently in development as a joint venture between Fortescue Metals Group, Formosa and Baosteel. It is supported by an extensive database of reverse circulation drill hole samples analysed by X-ray fluorescence (XRF), with a large subset tested for concentrate mass recovery, concentrate and tail grades by Davis tube recovery (DTR) testing. A limited number of rock physical testing results, including unconfined/uniaxial compressive strength and crushing work index, completes the database.By combining all available information – assays, DTR results, geology, stratigraphy, mineralogy and rock physical results – and using multivariate statistical analysis techniques, the impact of the critical factors that control concentrate quality, mass recovery and grindability characteristics have been outlined. A set of geochemical groups was created by using a cluster analysis technique from the combined XRF-DTR data. These groups allow optimal separation of material with consistently high concentrate Fe grades and mass recovery. This approach is superior to domaining based on stratigraphic logging or mass recovery as it is commonly used in standard magnetite estimation models. Using the results of a normative mineralogy study, the main geochemical groups were given a mineralogical profile fitting their geochemical characteristics. These findings further refined the understanding of the link between the process characteristics of the samples and their geochemical signature and mineralogy.The geochemical grouping defined on head grades and DTR concentrate mass recovery was generalised into a ‘geomet’ code based solely on the routinely assayed head grades, thus bypassing the need for systematic DTR testing. The geomet code identifies spatial domains with homogeneous geochemistry, mineralogy and process characteristics in both oxide and fresh material that form the basis of the current Iron Bridge resource model. The allocation of geometallurgical characteristics in terms of concentration amenability and concentrate characteristics on a block-by-block basis over the whole project allows for an optimum mine schedule and plant feed. This ensures that the desired concentrate characteristics and mass recovery can be better predicted over the life-of-mine, thereby improving the mine’s economics and stability by derisking the mine schedule and optimising the performance of the concentrators. A key benefit of the geomet code devised for the Iron Bridge mine is that it can be attributed in an automated manner to all samples analysed for a routine XRF analytical suite, from exploration to blasthole drilling. This allows each sample to be allocated to a geometallurgical material type with predictable process response in terms of concentrate mass recovery and concentrate quality without the need to complete systematic DTR testing.A standard multivariate analysis coupled with a cluster analysis has allowed the linking of interdisciplinary results between geology, mineralogy, geochemistry, process and metallurgy to better understand, predict and ultimately mine and process the Iron Bridge deposits. This allows plant operations and product quality to be optimised through each stage thanks to the predictable ore characteristics embedded in the mining model.CITATION:Manfrino, A, 2015. Unravelling the factors impacting on concentrate quality by geometallurgical data analysis at Fortescue Metals Group’s Iron Bridge magnetite mine, in Proceedings Iron Ore 2015, pp 567–578 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By Bryant Fitch

This paper will review thickening theory, from the ( ) of the practicing engineer, with particular emphasis on ( ) uncertainty or disagreement. It will attempt to outline broadly what we know and what we don't know. This should serve two purpose First, it will warn the process engineer where he might get into trouble. At least it will alert him to the risk involved in uncritically accepting any of the recommended design procedures. Second, it will identify for researchers some areas in which further work might be fruitful. Not too many years ago there would have been little to write on such a subject. We had been designing thickeners for decades, using the classic Coe and Clevenger procedure. As far as we were generally aware, they all turned out to be about the right size. And so if there was anything we didn't know, It certainly wasn't hurting us much. Today we know better. While it is true that in most cases units designed by the Coe and Clevenger procedure (1) will perform satisfactorily, we now know of cases in which they don't. And during the past few years there have been many developments and advances in basic thickening theory. So there is now a lot more room for disagreement, and a whole lot more to be uncertain about. What is "thickening" "Thickening" means different things to different people. For this paper we define it to mean sedimentation behavior characterized by line settling. Solids subside with a clear line of demarcation between settling solids and supernatant. Although the supernatant will usually be clear, in some cases it may be turbid. Line settling must entail that all particles just below the pulp-supernatant interface have the same subsidence rate, so that

Jan 1, 1971

By Glenn C. Miller

Cyanide is the most common lixiviant for extraction of precious metals, and its efficient use in open pit mines has contributed to the increase in world production of gold during the previous two decades. With this expansion of precious metals mining using cyanide, public concerns have developed in response to the inherent public perception of cyanide as a tox-in as well as a series of environmental problems that are directly or indirectly related to cyanide use in open pit mining. Some of these have technical or regulatory solutions, while others will require additional investigation before they can be resolved. The following discussion will summarize some of the public concerns regarding the use of cyanide in precious metals mining. The issue of cyanide use in large scale precious mining is controversial, and recent banning of cyanide use in open pit mines in Montana, or complete banning of cyanide in Hungary has reflected those international concerns. The underlying basis for some of the bans (e.g. Montana) reflect a general concern of the environmental impacts of mining, rather than specific issues related to risk of cyanide use. The human safety record for cyanide use, particularly in the developed countries is good, and cyanide is clearly the most efficient lixiviant for precious metals. Indeed, the relatively short lifetime for cyanide in the environment renders it one of the less problematic chemicals used for extraction of gold from ore. Mercury amalgamation or use of bromide as a lixiviant are certainly much more problematic. What, then, is the basis f~r the international concern about precious metals mines that use cyanide. Ifuse of cyanide for gold recovery is to continue, what additional infom1ation needs to be developed that will allow a better management of the risks of cyanide? Which of the concerns are directly related to cyanide, and which are indirect concerns that more related to effects of open pit mining. Under what conditions should use of cyanide be discouraged? DUl::ing June of 2000 the United Nations Environmental Program conducted a two-day workshop on cyanide use in mining that was attended by persons from the mining industry, regulators and environmental community. Support and attendance at this workshop reflected concerns by all three groups on further restrictions for cyanide use and the emerging potential for guidelines for better management of the catastrophic release of cyanide-containing mining waste. The following discussion is meant to focus-on those risks and explore the basis for an often negative reaction to precious metals mining using cyanide. It is presented in the format of a statement, followed by a discussion. While admittedly provocative, the statements are meant to express the concerns? of the public regarding cyanide and the mining industry.

Jan 1, 1998

By S. Lin

Fan stall is a notorious phenomenon with axial-flow fans. When multiple fans of this type serve a ventilation system, their mutual impacts are very complicated and not well understood. Results from laboratory experiments indicated that the immediate consequence of a fan working across its stall zone (i.e., the pronounced trough on the fan characteristic curve) is that some branches in the system may suffer abrupt and even drastic changes in air quantity and pressure. The quantity range of the fan that causes the abrupt change is called an unstable operating range. The corresponding quantity range of a branch is called a non-achievable quantity range of the branch because any quantity within this range cannot be achieved without changing some parameters of the ventilation system (e.g., branch resistances). These concepts are introduced based on the test results from tubing networks to bring attention to these important characteristics of ventilation systems.

Jan 1, 1996

By Ping Zhang, Xu Ma

Perturbations arising from mining operations significantly affect the stability of rock masses, and the influences aggerates with the rapid increase of mining-operation depths during recent years. The subsurface structures with major discontinuities subject to seismic hazards resulted from the shear-slip behaviors of rock masses. In order to identify the shear-slip regime of discontinuities and calculate seismic moment and seismic energy involved with shear-slip behaviors, we use discrete element modeling to study the shear slip failure along discontinuities in an underground mine. The recorded characteristic and properties of sub-contacts in DEM provide a basis for computing and visualizing the temporal and spatial distribution of seismic moment and seismic energy with mining operations. We computed the seismic energy and seismic moment using the numerical modeling method and the analytic method. We compared the result of summing seismic energy and seismic moment from the subcontacts of numerical models and the result of the analytic method. We confirmed that this tool can be used in comparative analyses. We also found that seismic moment and seismic energy, associated with shear stress drop and shear displacement increase, accumulate in the vicinity of major discontinuities. Mining operations at a greater depth cause greater changes of seismic moment and seismic energy, leading to a higher risk of inducing seismic hazards. Quantifying seismic potential using discrete element modeling can greatly facilitate the investigation of instability of geological discontinuities and thereby can help estimate the potential of seismic hazards.

Jan 21, 2023

By Thomas T., Read

THROUGHOUT the Colonial era, Philadelphia was easily , the leading city of North America, and it still held that position at the end of the period, with a population of about 25,000, though closely pressed by Boston, which had slightly over 20,000, and New York, which had nearly as many. It was the center of a region in which mineral industry was important. Thomas Rutter's bloomery, built in the Schuylkill valley in 1716, was quickly followed by many others, and during the Colonial period at least 20 blast furnaces, 45 forges, and iron- works of other types were built in eastern Pennsylvania, which easily led all the other colonies in iron manufacture. During the Revolutionary period others were erected as far west as Fort Loudon, in the Cumberland c alley.^ After 1800 the rapid development of the anthracite mining industry profoundly affected Philadelphia's, development, since transportation of the coal was then necessarily by water, and the streams of the anthracite . regions mostly flowed into either the Schuylkill or the Delaware Rivers. With an abundant near-by supply of coal and iron, with the seat of government, which had been there since 1774, and with a National Bank established there in 1791, one would have seemed safe in prophesying, at the beginning of the nineteenth century, that Philadelphia would permanently remain the leading city of the United States. Education in Philadelphia was at first wholly in the hands of the Quakers, who had established a "Public School" there in 1689, but in November 1739 George Whitefield, who had created a sensation in England by his preaching, though only 24 years old, passed through Philadelphia on his way to Georgia to found an orphan school there. He preached a series of sermons in Christ Church that were so disturbing to the established church that on Nov. 25 the Rev..Richard Peters (who was also Provincial

Jan 1, 1941